Sensitivity of our results to the PCA-like contaminant subtractions as function of how many modes have been removed from the original cube. In the top panel, we show the reduced χ² for each foreground cleaned cross-power spectra relative to its best-fitting model; in the bottom panel, the corresponding best-fitting Ω_H I b_H Ir values and their 1σ error bars. Filled symbols, circles and squares, are for an SVD a PCA cleaning respectively; their weighted counterparts corresponds to empty triangles and diamonds. In the bottom panel, the shaded red region highlights the CL23 best-fitting value and 1σ uncertainty that was obtained with a PCAw N_fg = 30 cleaning and a 𝒯-correction (the ‘uncorrected’ CL23 amplitude would lay between 0.2 − 0.3 × 10⁻³). We highlight in grey the N_fg = 4 results that correspond to our best and reference PCA result: the smallest N_fg to reach a plausible χ².